Task 2C Computation of Transport in PME I. Flow and Pollutant Transport

1. Chris Sideroff Thong Dang July 26, 2006 Task 2CComputation of Transport in PMEI. Flow and Pollutant Transport

2. “Better” IAQ • P.O. Fanger, SU June 06 • “Healthy Indoor Air, i.e. complete well being, requires more than 20 times higher IAQ” • “A paradigm shift is required” • For high IAQ need to address: • Source control • Air-cleaning • Personal ventilation Fanger: “Improve quality of breathed air by factor of 10” Fanger SU Lecture June 2006

3. Overview • Ventilation systems other than the mixing type (e.g. personal, displacement), flow/contaminant gradients are important – cannot use “well-mixed” assumption • Flow/contaminant gradients near manikin are important if prediction of human exposure to contaminants is of interest • Topp et al. 2002 • Personal Micro-Environment (PME): region around person which affects her/his breathed air – PME not a well-mixed environment • Interaction of the PME and surrounding environment is a complicated problem and requires accurate tools to tackle it => Task 2 “… when interested in the local air movements around occupants, the results show that a more detailed CSP should be applied as the local velocities were found to be different for the two CSP investigated.”They go on to say “… the local flow plays a role in the transport of contaminants to and from the breathing zone and, thus, the personal exposure”

4. Approach Characterize and assess IAQ (PME) using Computational Fluid Dynamics • CFD is a potentially efficient (fast/inexpensive) and flexible tool because of advancements in CFD methodologies (modeling of complex geometry and transient problems, advanced RANS turbulence models and LES models) and computing hardware (e.g. parallel computing clusters) • Accuracy of CFD? Determine whether RANS/LES CFD is capable of characterizing/ assessing the PME  EPA02 • Develop procedures/guidelines to use CFD for PME  EPA02 • Use CFD to increase fundamental knowledge of PME (and IAQ) and as a design tool when theory and/or experiments can not be applied => EPA03

5. Collaboration Provide Gaseous Conc. for BC’s Provide PM Conc. For BC’s Enhanced Validation and PM measurement Provide Guidelines for PEL CFD Task 1 Source Char. Task 2C Detailed CFD Task 2A Resusp. Exp. Task 2B Detailed Exp. Task 5A PEL Exp.

6. Current State-of-the-Art • In open literature, grid resolutions are typically on the order of a few hundred thousand (for 3D) • Traditional turbulence models • zero-equation (mixing length) • k-e family • Single-point, omni-directional measurements • velocity magnitude, no components • no turbulence information (length scale, intensity) • better error estimation • Steady-state • if breathing, steady inhalation/exhalation • no motion • Active research group at ASHRAE and Indoor Air – e.g. ASHRAE Chicago (Feb. 2006) Benchmark Symposium (Nielsen, Kato, Chen)

7. EPA03: Realistic Conditions • EPA02 - steady-state validation done • Using validation guidelines proceed to assess exposure under more realistic conditions • Unsteady breathing • Head motion (rotation) • Body motion (rotation) • Foot motion (tapping) • Further validate CFD for realistic setups with T2B (body rotation) • Some important consequences • Difference between exposure in these situations and those using steady-state assumption • Fundamental impact of these effects on the flow (e.g. thermal plume, origin of inhaled air, etc)

8. Breathing • Breathing is a transient process however a common assumption is to assume steady inhale or exhale • Important issues: • Difference in exposure (gaseous contaminant) – is the steady assumption sufficient? • Origin of breathed air – this information could help design of PME • Model the breathing cycle with a sinusoidal curve Actual (Marr T2B) Sinusoidal

9. Breathing • Breathing is a transient process however a common assumption is to assume steady inhale or exhale • Important issues: • Origin of breathed air – could help in design strategies of PME Transient Breathing Steady Inhalation Air comes from in front of lower torso region – _not_ directly from feet Origin of air: Stationary, Breathing Manikin Movie Gao & Nui 2004

10. Breathing • Breathing is a transient process however a common assumption is to assume steady inhale or exhale • Important issues: • Difference in exposure (gaseous contaminant) – is the steady assumption sufficient? Currently under investigation • T1A (Zhang - Source characterization) provides information for gaseous contaminant boundary conditions (concentration and/or flux) Emissions from clothing Front-cut Side-cut

11. Rotating Head 45° Right 22° Right Centered 22° Left 45° Left • People typically are not completely stationary for long periods of time • Rotation of head mimics a person reading • Important issues: • Origin of breathed air – how much does the motion affect where/what we breath? • Difference in exposure compared to 1) breathing alone 2) steady-state Breathing, Head Rotating Manikin Movie

12. Body Rotation IFL T2B Setup • Large scale motions of people my affect more than small breathing zone – e.g. person swiveling in an office chair • In parallel with T2B (Glauser) => enhanced validation • Important issues • Does this type of motion disturb the room flow enough to create enhanced mixing, i.e. will it cause the transport of contaminants not otherwise possible? • Fundamental impact of these effects on the flow (e.g. thermal plume, origin of inhaled air, etc)

13. Foot Motion • The interaction of a foot approaching the floor has been shown (SU work by Khalifa and Elhadidi 2005) to be an important mechanism in particulate matter (PM) resuspension • Simulation of actual motion (rotation & translation) of 3D foot is beyond our capability therefore a model was created that can recreate the flow from a foot approaching a flat surface • We suspect the flow created by this interaction will be an important factor in transport of pollutants and PM (T2C Ahmadi) away from the floor and eventually into the breathing zone (T2B Higuchi) Full 3D foot Axi-sym. 2D Piston Body-force Model

14. Foot Motion • Using the guidance of T2B (Higuchi - piston exp.) and CFD, momentum source constructed mimicking the external flow cause by a falling foot • Simulate transport of PM from falling foot – Boundary conditions for PM (loading and concentration) from T2A (Ferro)

15. Summary and Continuing Work • Capturing the flow/contaminant gradients are important forPME, hence detailed CFD required • Realistic details of a person in their PME are important - Investigation on the impact of the transient details (breathing and motions) is currently in progress • Interaction and collaboration with others relevant tasks (T1A, T2A, T2B, T5A) critical for success of detailed simulations